SENATE BATTLEGROUND MAP: The race for control of the Senate is as tight as it can be

Entering the midterms, Republicans hold a 51-to-49 seat majority in the upper chamber of Congress.

A few seats changing hands could flip the body to Democratic control.

But Democrats are faced with a challenging map.

The battle for control of the Senate is as tight as can be, and we're about to find out whether Republicans hang on to control of the chamber or whether Democrats can earn an unlikely flip.

As of Tuesday, candidates are separated by 3 points or less in five races, according to RealClearPolitics.

Polling shows Republican candidate, Rep. Kevin Cramer building his lead over a Democratic incumbent, Sen. Heidi Heitkamp, in North Dakota. In Missouri, Republican Josh Hawley holds a slim lead over another Democratic incumbent, Sen. Claire McCaskill.

Meanwhile, Democratic candidates Kyrsten Sinema and Jacky Rosen have been teetering in and out of the lead for the seats currently under GOP control in Arizona and Nevada.

In five states won by President Donald Trump in 2016, Democratic incumbents hold substantial leads over their opponents: Sens. Sherrod Brown of Ohio, Bob Casey of Pennsylvania, Joe Manchin of West Virginia, Debbie Stabenow of Michigan, and Tammy Baldwin of Wisconsin.

Entering the midterms, Republicans hold a 51-to-49 seat majority in the upper chamber of Congress. Depending on which way races go on Election Day, the makeup of the Senate could drastically change in the new year.